1. Field of the Invention
The present invention relates to a device, a method and a program for extracting a tubular structure, such as a blood vessel, from an image of a subject and searching for the shortest path in the extracted tubular structure.
2. Description of the Related Art
In recent years, along with the advancement of medical equipment (such as a multi-detector CT), high quality three-dimensional images are being used in imaging diagnosis. However, since a three-dimensional image is formed by a number of two-dimensional images and thus has a large volume of information, it may take a long time for a doctor to find a desired site to be observed and diagnose the site. Therefore, an organ of interest is extracted and displayed as a MIP image, a VR image, a CPR image, or the like, to increase visual recognizability of the entire organ and the lesion, thereby increasing the efficiency of the diagnosis.
On the other hand, in order to obtain effective information for diagnosis, such as a CPR image developed along a path of a blood vessel, a site of stenosis and a stenosis rate, when an analysis of cardiac CT images, in particular, an analysis of the coronary arteries or an analysis of the cerebral blood vessels is performed, the center path of the blood vessel, such as the coronary arteries, is extracted as a graph structure from a three-dimensional image containing tubular structures and is displayed. For example, Japanese Unexamined Patent Publication No. 11 (1999)-120327 (hereinafter, Patent Document 1) proposes a technique that involves extracting, from an area between the start point and the target site in a tubular structure, such as a blood vessel, a plurality of center lines running through the center of the tubular structure and leading to the target site, searching for the shortest path from the center lines, and displaying the shortest path superimposed on a displayed image of the corresponding tubular structure.
With the technique disclosed in Patent Document 1, however, the center line may be interrupted at a portion of the blood vessel that is narrowed due to plaque, or the like, or a portion of the tubular structure where a tissue, such as fat, that is different from the tubular structure is deposited. When the center line is interrupted, the shortest path search cannot be achieved. In order to address this problem, a technique that involves receiving a specification of an interrupted portion by the user if the center line is interrupted, and connecting the interrupted portion to enable the shortest path search is proposed (see U.S. Patent Application Publication No. 20040249270 (hereinafter, Patent Document 2)).